Abstract
BACKGROUND: Cysteine is a glutathione precursor, but is also a homocysteine byproduct. We prospectively evaluated relationships between fasting plasma concentrations of total cysteine and total homocysteine, and subsequent myocardial infarction (MI) in women. METHODS: Among 32,826 women who provided blood samples between 1989 and 1990, 239 were diagnosed with incident MI after blood collection, but before July 1998. Of these women, 144 had provided a postfast sample. We matched controls to cases 2:1 by age, cigarette smoking status, and month and fasting status at the time of blood collection. We used conditional logistic regression to adjust for confounding. RESULTS: Fasting total cysteine was positively related to MI risk in matching factor-adjusted analyses (rate ratio [RR] for highest vs lowest quartile 3.50 [95% CI 1.44-8.52]). However, after controlling for conventional risk factors of MI, it was not independently associated with risk (RR for highest vs lowest quartile 1.32 [95% CI 0.42-4.12, P trend = .10]). Fasting homocysteine was positively associated with MI risk; the multivariable adjusted RR for the highest versus the lowest quartile was 3.37 (95% CI 1.30-8.70, P trend = .014). CONCLUSIONS: Fasting plasma concentration of total homocysteine, but not total cysteine, was positively associated with MI risk.